This clasp, also called an unfolding buckle clasp, is well known in the state of the art and usually includes one or two push buttons as the fastening system. However, a lever has sometimes been proposed to replace the conventional push buttons and it is this that will be developed by the present invention.
A clasp implementing a control lever and broadly matching the brief description given hereinbefore is disclosed in EP Patent No. 1654950. This clasp includes at least two branches articulated to each other by one of the respective ends thereof. One of the free ends of these branches includes a lever articulated about an arbour parallel to the axis of articulation of the branches and integral with a hook, the other free end of these branches including a hooking element shaped to enable the hook to engage therewith to hold the branches in the folded position. The lever includes elastic means for exerting torque thereon and stop means for limiting the pivoting thereof, via the effect of the torque, about said arbour, in a position corresponding at least to the engagement of the locking hook with the hooking element, wherein the elastic means are biased, such that the lever has to pivot against the elastic means to engage and to release the locking hook from the hooking element.
In this prior art document, it is clear that the lever must be raised in order to open the clasp, which is quite natural and expected, but the lever also has to be raised in order to close and lock the clasp, which complicates the closing operation and makes it tedious. It is an object of the present invention to make it unnecessary to handle the control lever during the closing operation and to propose a design that achieves this object.